Location: Earth-8810, an
alternate future @ 20 years after the modern era. The bubble
itself existed over a span of 15 years.

Powers/Abilities/Functions: The Time Bubble is
associated with an immense black hole, feeding an even more immense
Galactus. It grew so large that it threatened to destroy the entire
universe, and the pull was so powerful that it warped time around it,
making time travel into the past or future beyond it virtually
impossible. The surface of the Bubble possesses an unbelievably
powerful probability flux. Most who tried to penetrate it were either
violently destroyed or simply ceased to exist.
The time warp within the Bubble brought all time in
that universe to a virtual halt, with only Galactus and those
possessing probability generators able to move. Gladiator was able to
achieve a hyper-speed that allowed him to interact with those
possessing said generators.

History:
(Fantastic Four I#340 (fb)) - The Time Bubble originated in an
alternate Earth dimension. When Galactus nearly died on Earth, the
Black/Dreaming Celestial altered Galactus' makeup, restoring him, but
altering him, such that his hunger had become ravenous, and his
appetite increased geometrically. The Black Celestial's intent was that
Galactus would eventually consume the entire universe, including the
other Celestials, as well. Meanwhile, the Black Celestial summoned an
army of Deviants to construct machineries of probability that would
ensure that they would still exist when all else had become void. The
Black Celestial would then become the nucleus and founder of a new
reality.

(Fantastic Four I#338 (fb) - BTS) - As Galactus grew
in size, he eventually utilized a machine which generated a black hole,
drawing more and more mass into itself, which in turn caused both it
and him to grow in size, and his hunger increased as well. Eventually,
around twenty years after the modern era, the force generated by this
massive black hole began to warp time around it.

(Thor I#372 (fb) - BTS) - Investigating the
time warp, the Time Variance Authority
unwittingly exacerbated it, creating a 15 year bubble of time around
it. This bubble eventually extended across all timelines, limiting time
travel in either direction past that point.

(Avengers I#295 (fb) - BTS) - The Council of Cross-Time Kangs learned of the existence of the Time Bubble, and recognized it as containing a weapon of some sort.

(Avengers I#296 (fb)) - A trio of Kangs attempted to penetrate the Time Bubble, and they were lost forever.

(Avengers I#296 (fb)) - An occasional low probability
anomaly in the time flux enabled the Council of Cross-Time Kangs to
obtain some imaging from within the bubble. They learned of the
involvement of the Black Celestial and of the existence of his massive
weapon at the center of the bubble.

(Avengers I#295 (fb) - BTS) - Infiltrating the Council of Cross-Time Kangs, the Terminatrix,
then known as Kang-Nebula, learned of the Time Bubble, and began to
seek out the weapon. She--and the Council--came to believe that the
Avengers would be the ones to pierce the Time Bubble.

(Avengers I#291-295 - BTS) - Kang-Nebula began to take steps to manipulate the Avengers, starting with Dr. Druid, and gradually gaining control of the lot of them.

(Avengers I#296) - As Kang-Nebula manipulated the
Avengers toward investigating the Bubble, the Council of Kangs, who
wanted the Bubble as well, sent a trio--Chairman Kang, Kang of
Earth-123488 (infinitely repeating 8s), and Kang of Earth-Mesozoic--to
try to prevent her from claiming the weapon, so that the Kangs could
have it themselves.
Nebula, along with the Avegners (Black Knight, Dr.
Druid, She-Hulk, and Thor), traveled forward (and across) time,
approaching the Bubble, itself.

(Avengers I#297) - Maximizing the power of her
temporal equipment via Thor's hammer, Kang-Nebula led the Avengers to
pierce the surface of the Time Bubble, though the trio of Kangs managed
to latch on to and ride their ship. As they continued to penetrate the
Bubble, the Kangs managed to neutralize Kang-Nebula's control over the
Avengers, and the Black Knight, She-Hulk, and Thor turned on her.
Without Kang-Nebula's guidance, their Quinjet skimmed back out of the
Bubble. Kang-Nebula was cast from the ship and pulled into a temporal
vortex, and Dr. Druid leapt in after her.

(Fantastic Four I#341(fb) - BTS/337) - Reed Richards
discovered the Time Bubble as it effectively blocked time travel past
it across the realities. Kang-Nebula had her agents send a bomb to slay
the Fantastic Four, and when Reed neutralized the bomb, she recognized
that he would be the one to actually pierce the Bubble. Using his
Radical Dodecahedron, Reed powered their timesled Rosebud II, with
which the FF (assisted by Iron Man and Thor) entered the zone around
the Bubble, generating hundreds of divergences in the process (or
perhaps just showing hundreds of divergent timelines converging on a
single point).

(Fantastic
Four I#338) -
The above-mentioned trio of Kangs, as well as Kang-Nebula, latched onto
Rosebud and were drawn into the interior of the Time Bubble with the
FF. The Kangs were destroyed with the aid of Death's Head,
who was banished from the Time Bubble when a blast from one of the
Kangs damaged his craft's probability generator. As they headed for the
nexus of the Bubble, they observed the mammoth form of Galactus and
recognized his involvement.

(Fantastic Four I#341(fb)/339, 340) - The FF tried to
destroy the device generating the black hole via the weapons cache of
the entire Shi'ar empire, aided by Gladiator, but the Black Celestial
revived and teleported the weapons directly into the black hole,
destroying it in one fell swoop. Journeying to the Earth of that
reality, Reed duped the computer of the Black Celestial into revealing
his origins. Gladiator then crashed the remaining floating weapons
depot into the Black Celestials' base, destroying it and apparently
himself. However, Sue and Johnny, assaulted by Kang-Nebula, were
trapped there and seemingly destroyed in the explosion, but Kang-Nebula
had activated Sue's force field to save them all.
Meanwhile, a vengeful Reed taunted the Black
Celestial with his plans to travel back in time and inform his brethren
in the Celestials of his plans, so that they might stop him before he
ever brought them to fruition. Teleporting back and forth with the
space of that universe and within the time period of the bubble, Reed
allowed the Black Celestial to grow ever closer to them, until they led
it to the point of no return from Galactus' event horizon/black hole.
At the last second, Reed signaled Thor to form a magical warp to
teleport them a safe distance away, while the Black Celestial was
pulled into and destroyed by the black hole.
For a brief instant, Galactus' raging appetite (and
thus his sanity) were appeased, but this soon passed, and the
consumption occurred at an even more accelerated rate from the vast
influx of mass and power of the Celestial.

(Fantastic Four I#341) - Happy to learn of Sue and
Johnny's survival, Reed led the group to Taa II, Galactus' worldship,
where he located the Ultimate Nullifier. Kang-Nebula had been
possessing Sue, and she attempted to usurp the Nullifier, but she fell
for a trap set by Iron Man under Reed's direction, as Reed had
suspected her involvement. Stunned by the electrical shock, Kang-Nebula
was forced out of Sue and lost into the atmosphere of the Bubble.
Returning to Galactus, the combined full energies of Thor, Iron Man,
and the Torch's nova flame briefly restored Galactus' sanity, and he
recognized the Nullifier as Reed gave it to him. Wishing to end his
torment, Galactus activated the Nullifier, and a sphere of nothing
consumed him and then the entire universe, effectively destroying the
Time Bubble.
The FF and their allies narrowly escaped the
destruction, and when Thor and Iron Man fell off the timesled (back to
Earth-616), the FF instead arrived in Earth-Stalin Robot.

Comments: Created by Walt Simonson, with
John Busema.

I was going to do a whole profile
on Earth-Time Bubble, but in the interest of expediency, I'm just doing
the Bubble itself for now. It's got all of the important info, but not
a bunch of sub-profiles. Earth-Time Bubble diverged from Earth-616 in
Fantastic Four I#244, in theory, but the events could have happened in
Earth-616, as well, and just not been actualized yet...or neutralized
during one of Galactus' deaths.

Simonson seemed to have intended
"Kang-Nebula" to be the same Nebula as the space pirate who claimed to
be the descendent of Thanos. Later stories ret-conned her into being a
counterpart of Ravonna, and renamed her the Terminatrix.

Simonson's whole run on the FF is
my second favorite's (after Byrne's), but this Time Bubble saga is
probably my favorite FF story, ever. I loved the time travel technology
jargon, like "redundancy existentialators," "Heisenberg Effect
neutralizers," the Kurtzberg drive (after Jack Kirby), and the
mathematical papers of Lieber (after Stan Lee)/Kurtzberg.
And, of course, Rosebud II is after Rosebud, the sled from Citizen
Kane. That's PROBABLY what inspired someone to come up with the Citizen
Kang storyline.
And then Thomas gives Simonson his props during the Timequake saga in What If?, when the TVA registers a timequake on the Simonwalt scale.

I don't think there would be other
divergent forms of the Time Bubble still in existence. The converging
alternate versions of the FF and Avengers as they approached the Bubble
would make it seem that only one of them existed. Regardless, however,
there are only two basic possibilities. One, that the Bubble was
destroyed in which it would no longer exist, and two, that Galactus did
not accept the Nullifier (or was otherwise not destroyed), in which
case, he would eventually have consumed that entire universe. Whether
or not Galactus and the Time Bubble would have then destroyed
surrounding realities or even the entire Multiverse or Omniverse is
debatable, and presumably academic at this point.